<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>省市</title>
</head>
<body onload="init_data()">
    <div id="outer">
        <select id="province" onchange="change_city(this)">
            <option value="-1">===选择省份===</option>
        </select>
        <select id="city">
            <option value="-1">===选择城市===</option>
        </select>
    </div>
    <script>
        let provinces = ["江苏省","安徽省"];
        let citys = [["徐州","宿迁","连云港","泰州","南京","苏州","常州","扬州","无锡","南通","镇江"],["滁州","蚌埠","六安","芜湖","合肥","宿州","黄山"]];
        function init_data(){
            //数据的初始化操作.
            let province
        }
    </script>
</body>
</html>